Trans-1-chloro-3,3,3-trifluoroproprene (HCFO-1233zdE) is a product with a low global warming potential (GWP). It has thermodynamic and thermophysical properties that are very favorable for use as a heat-transfer fluid in cooling, air-conditioning, electricity production (in particular by means of organic Rankine cycles) and high-temperature heat pump applications.
HCFO-1233zdE has an instability which manifests itself especially at relatively high temperature. This instability consists of an isomerization of a fraction of the initial feedstock resulting in the formation of cis-1-chloro-3,3,3-trifluoroproprene (HCFO-1233zdZ).
As it happens, HCFO-1233zdZ is a less volatile product than HCFO-1233zdE. The boiling point is about 40° C. for the Z isomer, and about 18.3° C. for the E isomer. This difference implies a change in the thermodynamic and thermophysical properties of the product in facilities, and a loss of performance level, when the isomerization occurs.
Document WO 2009/003165 describes the risks of degradation of hydrofluoroolefins and hydrochlorofluoroolefins, and also stabilizers for combating this degradation. These stabilizers comprise free radical scavenger compounds, acid scavenger compounds, oxygen scavenger compounds and polymerization inhibitors. Mention is in particular made of: 1,2-epoxybutane, glycidyl methyl ether, d-1-limonene oxide, 1,2-epoxymethylpropane, nitromethane, alpha-methylstyrene, isoprene, phenol, hydroquinones and hydrazine.
Document U.S. Pat. No. 7,795,480 describes a process for producing 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf). A phenomenon of polymerization of the compound is mentioned (but not an isomerization phenomenon). Proposed stabilizers are p-tap(4-tert-amylphenol), methoxyhydroquinone, 4-methoxyphenol, triethylamine, diisopropylamine, butylated hydroxyanisole and thymol.
Document U.S. Pat. No. 8,217,208 describes the phenomenon of isomerization of HFO-1233zdE under the effect of temperature, but it does not teach stabilizers which make it possible to limit this isomerization.
Document US 2012/0226081 describes the risks of degradation of hydrochloroolefins and of hydrochloroalkanes, and proposes a set of possible stabilizers: alpha-methylstyrene, alpha-pineneoxide, beta-pineneoxide, 1,2-epoxybutane, 1,2-hexadecene oxide and oxygen scavenger compounds such as diethylhydroxylamine, hydroquinone, methylethylketooxime and p-methoxyphenol.
Document US 2015/0034523 describes the risks of degradation of hydrochloroolefins and proposes two families of stabilizers, namely morpholines or trialkyl phosphates.
Virtually all of the stabilizers proposed in the prior art are solid products, or liquid products with a high boiling point. For example, the boiling point of alpha-methylstyrene is 165° C., the boiling point of limonene oxide is greater than 200° C., etc.
Isoprene, mentioned in document WO 2009/003165, is for its part a product that is unstable in itself, and that must generally be combined with a compound such as 4-tert-butylpyrocatechol in order to prevent it from being polymerized.
The characteristics described above make the stabilizers unsuitable for certain applications in which HCFO-1233zdE is liable to be used. This is in particular the case with applications using flooded evaporators (in particular with compressors without lubricating oil). In such applications, the prior art stabilizers, with a high boiling point, are ineffective since they concentrate in the evaporator and do not migrate with the heat-transfer fluid to the condenser.
There is therefore a need to provide stabilizers which make it possible to limit or prevent the isomerization of HCFO-1233zdE to HCFO-1233zdZ, in particular in vapor compression systems such as air-conditioning, refrigeration, heat-pump and organic Rankine cycle systems, and quite particularly systems comprising a flooded evaporator.